Assessing Malignant Risk in B3 Breast Lesions: Clinical Insights and Implications

Background/Objectives: B3 breast lesions, characterized by uncertain malignant potential, pose a significant challenge for clinicians. With the increasing use of preoperative biopsies, there is a need for careful management strategies, including watchful waiting, vacuum-assisted excision (VAE), and surgery. This study aims to assess the concordance between preoperative biopsy findings and postoperative histology, with a focus on evaluating the positive predictive value (PPV) for malignancy in B3 lesions. Methods: Over a seven-year period, 305 patients preoperatively diagnosed with B3 lesions were treated at the Multidisciplinary Breast Center of "Fondazione Policlinico Universitario Agostino Gemelli IRCCS" in Rome. All cases were reviewed at multidisciplinary meetings involving surgeons, radiologists, histopathologists, and oncologists. Preoperative diagnoses were obtained by ultrasound-guided core needle biopsies (CNBs) or stereotactic-guided vacuum-assisted biopsies (VABs). The radiological features were assessed using the Breast Imaging Reporting and Data System (BIRADS), and discrepancies between radiological and pathological findings were recorded. The biopsy results were compared with the postoperative histological findings to calculate the PPV for malignancy. Results: Of the 305 B3 lesions biopsied, 242 were confirmed as B3 on the final histological examination, resulting in a concordance rate of 79.3%. A total of 63 cases were upgraded to malignancy on postoperative histology, yielding a cumulative upgrade rate of 20.7%. The PPV for malignancy was 31.5% for atypical ductal hyperplasia (ADH), 27.6% for lobular neoplasia (LN), 22.9% for papillary lesions (PLs), 12.1% for flat epithelial atypia (FEA), 10.4% for radial scar (RS), and 10.3% for phyllodes tumors (PTs). Conclusions: Our findings demonstrate that the cumulative PPV for B3 lesions, as well as the PPV for each subtype, are consistent with the existing literature. The factors influencing the PPV include the use of CNB versus VAB, discordance between the BIRADS and biopsy results, the presence of atypia in the biopsy sample, the presence of microcalcifications on mammography, mass lesions identified on MRI, and the extent of the lesion. These factors should be considered in the personalized management of B3 lesions, potentially leading to more targeted and less invasive approaches in the future.